Regional nerve blocks are used as an anesthetic technique for surgery and pain control, and can be used in some instances as an alternative to general anesthesia and the complications that often result. For example, general anesthesia requires artificial respiration and often produces post-operative nausea and vomiting that complicate recovery. General anesthesia also includes a risk of post-operative hemodynamic or pulmonary depression, and in some patients it can create post-operative cognitive dysfunction. Regional nerve blocks have been shown to improve anesthesia and analgesia management, and to contribute to earlier ambulation after surgical procedures. In addition, a regional nerve block can provide continuous pain management when needed.
The administration of a regional nerve block involves the injection of an anesthetic to a target nerve, which provides anesthesia to a region distal to that nerve. Unfortunately, locating the target nerve and properly administering the anesthetic can be difficult. For example, a properly administered regional nerve block involves the injection of the anesthetic around—but not into—the target nerve. If the drug is not injected into the area immediately surrounding the nerve, the level of anesthesia required for the intended treatment (e.g., surgery, etc.) may not be achieved. Such a situation delays the procedure and subjects the patient to the risk of inadequate pain control. As noted above, it is also important to avoid inserting the needle directly into the nerve itself because trauma or damage to the nerve may occur. Another challenge involved in the performance of a regional nerve block is avoiding the puncturing of a blood vessel.
A conventional method for locating a target nerve involves the palpation of anatomical landmarks such as muscles, bones and blood vessels by the treatment provider (e.g., a doctor, physician's assistant, nurse, etc.). This method is inexact because of individual variations in patient anatomy and because the target nerve can move as the needle is being inserted. The difficulty in accurately locating the target nerve has been a factor limiting the use of regional nerve blocks.
Ultrasound technology has been used to image various parts of patient's bodies, but the use of an ultrasound imaging device by itself in connection with the administration of regional nerve blocks has met with limited success. For example, a limitation of ultrasound is that it can be difficult in some situations to see the needle or needle tip precisely. It can also be difficult to differentiate the nerve in the image from surrounding structures, such as blood vessels. Also, ultrasound does not provide the level of localization specificity that is provided by the motor or sensory response of Electrical Nerve Stimulation (ENS).
ENS applies an electrical stimulation current across the target nerve to produce a response in the patient such that the treatment provider (i.e., a physician, technician or the like) can accurately locate the nerve. In ENS, the needle that ultimately delivers the anesthetic to the area surrounding the target nerve has a conductive electrode area located at its tip to provide a precise localization of the stimulus. The remainder of the needle is electrically insulated. Another electrode is applied transcutaneously and distal to the needle insertion site. The treatment provider can then cause an electrical current to flow between the electrodes to stimulate the area between the electrodes. If the needle is within a certain distance of the target nerve, the current will cause a response in the nerve, thereby indicating that the needle is in proper position for administration of the anesthetic.
However, conventional ENS also has drawbacks that limit its effectiveness. For example, a treatment provider typically uses palpation or another method to make an educated guess as to the location of the nerve when placing the needle. Thus, additional movement of the needle—which may be uncomfortable for the patient—may be required to place the needle in a proper position for administration of the anesthetic.
Because of the drawbacks of using ultrasound or ENS alone, treatment providers often use both techniques to perform a nerve block. In such an arrangement, the treatment provider uses the ultrasound device to image the nerve—thereby enabling an accurate initial positioning of the needle—and then uses the ENS electrodes to evoke the nerve response to confirm that the needle is in proper position.
Unfortunately, when the two techniques are combined, the treatment provider is required to set up, control and view two separate instrument displays, which is cumbersome and difficult to perform when simultaneously attempting to position a needle in a patient's body. Operating the ultrasound and stimulator controls to perform a nerve block is complicated by the fact that the procedure usually takes place in a sterile field.
For example, a conventional ultrasound machine has a probe that operates within the sterile field and a main unit that operates outside the sterile field. The main unit may be enclosed in a plastic cover to enable it to be located within the sterile field, but in such cases the treatment provider is limited in the adjustments that can be made using the controls of the main unit. More often, a second person may need to operate the main unit while the treatment provider uses the probe. Likewise, a conventional ENS device may include a transcutaneous and percutaneous electrode that operate within the sterile field, and a main unit that operates outside of the sterile field.
Therefore, a treatment provider that uses both an ultrasound and ENS device in connection with a nerve block may need to perform any of the following tasks simultaneously: positioning the ultrasound probe while viewing the ultrasound display, adjusting an ultrasound device setting, positioning the needle, activating the transcutaneous and percutaneous electrodes, adjusting the electrode settings, viewing the electrode settings on a ENS device display and administering the anesthetic. It can be seen that such a wide range of tasks involving more than one medical device (i.e., a separate ultrasound and ENS device) can be extremely difficult for a single person to perform.
Therefore, what is needed is a device that integrates the functionality of an ultrasound and ENS device into a single device. More particularly, what is needed is an integrated ultrasound and ENS device that is adapted for a treatment provider to use while in a sterile field.